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Reach:   The Safest and Easiest DApp Programming Language
0.1.5

Reach: The Safest and Easiest DApp Programming Language

Jay McCarthy <jay@reach.sh>

Reach is a domain-specific language for building decentralized applications (DApps).

This set of documents contains everything you need to know about Reach.

If you are looking for something specific, here are some places to look:

The source of this site is available on GitHub; we welcome Pull Requests for improvements and Issues for problem reports!

    1 Overview

      1.1 Decentralized applications

      1.2 A minimal Reach program

      1.3 Compile

      1.4 Verify

      1.5 Interface

      1.6 Execute

      1.7 Web app

      1.8 Next steps

    2 Tutorial

      2.1 Install and Initialize

      2.2 Scaffolding and Setup

      2.3 Rock, Paper, and Scissors

      2.4 Bets and Wagers

      2.5 Trust and Commitments

      2.6 Timeouts and Participation

      2.7 Play and Play Again

      2.8 Interaction and Independence

      2.9 Web Interaction

      2.10 Onward and Further

      2.11 Rock, Paper, Scissors in Python

    3 Guide

      3.1 Using Reach on Windows

      3.2 How does Reach use version numbers?

      3.3 How does Reach development compare to Solidity development?

        3.3.1 Solidity Development

        3.3.2 Reach Development

        3.3.3 Conclusion

      3.4 Do I have to use JavaScript to write my frontend? What about Python, Go, or other languages?

      3.5 How do I add tracing logs to my Reach program?

      3.6 How do network and non-network tokens differ?

        3.6.1 How do network tokens behave?

        3.6.2 How do non-network tokens violate this?

        3.6.3 Why does this matter?

        3.6.4 What does Reach do about this?

        3.6.5 What can I do about it?

      3.7 What do the different kinds of consensus transfers mean? publish, pay, race, fork, parallelReduce?

        3.7.1 Is a single participant responsible for the transfer?

        3.7.2 Are multiple participants able to cause the transfer, but each will provide different data?

        3.7.3 Are there multiple participants that each want to do different things?

        3.7.4 Will these different things happen over and over until some condition is met?

        3.7.5 Summary

      3.8 How and what to verify

      3.9 Finding and using loop invariants

      3.10 Non-participation: What it is and how to protect against it

      3.11 Determinism, simultaneity, and choice in decentralized applications

      3.12 Racing non-determinism in decentralized applications

      3.13 Building decentralized abstractions

      3.14 How to use Ganache with Reach

      3.15 IDE/Text Editor Support

      3.16 Sharing and discovering shared Reach packages

      3.17 How does Reach work?

      3.18 What are Reach’s limitations?

      3.19 Reach’s Roadmap

      3.20 Reach’s Changelog

        0.1.5: 2021/09 - present

        0.1.4: 2021/09 - 2021/09

        0.1.3: 2021/07 - 2021/08

        0.1.2: 2020/09 - 2021/07

        0.1.1: 2019/09 - 2020/09

        0.1.0: 2019/09 - 2020/09

    4 Workshop

      4.1 Workshop: Hash Lock

        4.1.1 Problem Analysis

        4.1.2 Data Definition

        4.1.3 Communication Construction

        4.1.4 Assertion Insertion

        4.1.5 Interaction Introduction

        4.1.6 Deployment Decisions

        4.1.7 Discussion

      4.2 Workshop: Relay Account

        4.2.1 Problem Analysis

        4.2.2 Data Definition

        4.2.3 Communication Construction

        4.2.4 Assertion Insertion

        4.2.5 Interaction Introduction

        4.2.6 Deployment Decisions

        4.2.7 Discussion and Next Steps

      4.3 Workshop: Trust Fund

        4.3.1 Problem Analysis

        4.3.2 Data Definition

        4.3.3 Communication Construction

        4.3.4 Assertion Insertion

        4.3.5 Interaction Introduction

        4.3.6 Deployment Decisions

        4.3.7 Discussion and Next Steps

      4.4 Workshop: Fear of Missing Out

        4.4.1 Problem Analysis

        4.4.2 Data Definition

        4.4.3 Communication Construction

        4.4.4 Assertion Insertion

        4.4.5 Interaction Introduction

        4.4.6 Deployment Decisions

        4.4.7 Discussion and Next Steps

      4.5 Workshop: Fear of Missing Out Generalized

        4.5.1 Problem Analysis

        4.5.2 Data Definition

        4.5.3 Communication Construction

        4.5.4 Assertion Insertion

        4.5.5 Interaction Introduction

        4.5.6 Deployment Decisions

        4.5.7 Discussion and Next Steps

      4.6 Workshop: Fair Rock-Paper-Scissors

      4.7 Workshop: Efficient Rock-Paper-Scissors

      4.8 Workshop: Rental Agreement

      4.9 Workshop: Simultaneous Games

      4.10 Workshop: Guardian Account

      4.11 Workshop: Periodic Payment

      4.12 Workshop: Nim

      4.13 Workshop: Tic-Tac-Toe

      4.14 Workshop: Secured Loan

      4.15 Workshop: Atomic Swap

      4.16 Workshop: Atomic Swap Auction

      4.17 Workshop: Race

      4.18 Workshop: Chicken

      4.19 Workshop: Popularity Contest

      4.20 Workshop: Simple NFT

      4.21 Workshop: NFT with Auction

      4.22 Workshop: NFT with Royalties and Harberger Tax

      4.23 Workshop: Raffle

      4.24 Workshop: Rent Seeking

      4.25 Workshop: Remote Objects

      4.26 Workshop: Oracle

      4.27 Workshop: Timed English Auction

      4.28 Workshop: Crowd-funding

    5 Reference

      5.1 Installation

      5.2 Usage

        5.2.1 reach compile

        5.2.2 reach init

        5.2.3 reach run

        5.2.4 reach down

        5.2.5 reach scaffold

        5.2.6 reach react

        5.2.7 reach devnet

        5.2.8 reach rpc-server

        5.2.9 reach rpc-run

        5.2.10 reach docker-reset

        5.2.11 reach upgrade

        5.2.12 reach update

        5.2.13 reach version

        5.2.14 reach hashes

      5.3 Language Model

        5.3.1 Evaluation Model

        5.3.2 Compilation Model

        5.3.3 Syntax Model

      5.4 Programs

        5.4.1 Validity and other concepts

          5.4.1.1 Security levels and scope

          5.4.1.2 Domination

        5.4.2 Modules

          5.4.2.1 Statements

            5.4.2.1.1 export

            5.4.2.1.2 import

              5.4.2.1.2.1 Local imports

              5.4.2.1.2.2 Package imports

          5.4.2.2 Expressions

            5.4.2.2.1 Reach.App

              5.4.2.2.1.1 Deprecated long-form

        5.4.3 Application Initialization

          5.4.3.1 Statements

            5.4.3.1.1 deploy

            5.4.3.1.2 setOptions

          5.4.3.2 Expressions

            5.4.3.2.1 Participant Definition

            5.4.3.2.2 View Definition

        5.4.4 Steps

          5.4.4.1 Statements

            5.4.4.1.1 only and each

            5.4.4.1.2 Pay Amounts

            5.4.4.1.3 publish, pay, when, and timeout

            5.4.4.1.4 fork

              5.4.4.1.4.1 fork intuition

            5.4.4.1.5 wait

            5.4.4.1.6 exit

          5.4.4.2 Expressions

            5.4.4.2.1 race

            5.4.4.2.2 unknowable

            5.4.4.2.3 closeTo

        5.4.5 Local Steps

          5.4.5.1 Statements

          5.4.5.2 Expressions

            5.4.5.2.1 this

            5.4.5.2.2 interact

            5.4.5.2.3 assume

            5.4.5.2.4 fail

            5.4.5.2.5 declassify

            5.4.5.2.6 makeCommitment

            5.4.5.2.7 didPublish

        5.4.6 Consensus Steps

          5.4.6.1 Statements

            5.4.6.1.1 commit

            5.4.6.1.2 only and each

            5.4.6.1.3 View Objects

            5.4.6.1.4 Participant.set and .set

            5.4.6.1.5 while

            5.4.6.1.6 continue

            5.4.6.1.7 parallelReduce

              5.4.6.1.7.1 .timeRemaining

              5.4.6.1.7.2 .throwTimeout

              5.4.6.1.7.3 parallelReduce intuition

          5.4.6.2 Expressions

            5.4.6.2.1 this

            5.4.6.2.2 transfer

            5.4.6.2.3 require

            5.4.6.2.4 checkCommitment

            5.4.6.2.5 Token minting

            5.4.6.2.6 Remote objects

            5.4.6.2.7 Mappings: creation and modification

            5.4.6.2.8 Sets: creation and modification

        5.4.7 Computations

          5.4.7.1 Comments

          5.4.7.2 Blocks

          5.4.7.3 Statements

            5.4.7.3.1 const and function

            5.4.7.3.2 return

            5.4.7.3.3 if

            5.4.7.3.4 switch

            5.4.7.3.5 Block statements

            5.4.7.3.6 Try/Catch & Throw Statements

            5.4.7.3.7 Expression statements

          5.4.7.4 Expressions

            5.4.7.4.1 ’use strict’

            5.4.7.4.2 unstrict

            5.4.7.4.3 Identifier reference

            5.4.7.4.4 Function application

            5.4.7.4.5 Types

            5.4.7.4.6 Literal values

            5.4.7.4.7 Operator expression

            5.4.7.4.8 xor

            5.4.7.4.9 Padding

            5.4.7.4.10 Parenthesized expression

            5.4.7.4.11 Tuples

            5.4.7.4.12 array

            5.4.7.4.13 Element reference

            5.4.7.4.14 Array & tuple length: Tuple.length, Array.length, and .length

            5.4.7.4.15 Array & tuple update: Tuple.set, Array.set, and .set

            5.4.7.4.16 Array element type: Array.elemType and .elemType

            5.4.7.4.17 Foldable operations

              5.4.7.4.17.1 Foldable.forEach && .forEach

              5.4.7.4.17.2 Foldable.all && .all

              5.4.7.4.17.3 Foldable.any && .any

              5.4.7.4.17.4 Foldable.or && .or

              5.4.7.4.17.5 Foldable.and && .and

              5.4.7.4.17.6 Foldable.includes && .includes

              5.4.7.4.17.7 Foldable.count && .count

              5.4.7.4.17.8 Foldable.size && .size

              5.4.7.4.17.9 Foldable.min && .min

              5.4.7.4.17.10 Foldable.max && .max

              5.4.7.4.17.11 Foldable.sum && .sum

              5.4.7.4.17.12 Foldable.product && .product

              5.4.7.4.17.13 Foldable.average && .average

            5.4.7.4.18 Array group operations

              5.4.7.4.18.1 Array.iota

              5.4.7.4.18.2 Array.replicate && .replicate

              5.4.7.4.18.3 Array.concat && .concat

              5.4.7.4.18.4 Array.empty

              5.4.7.4.18.5 Array.zip && .zip

              5.4.7.4.18.6 Array.map && .map

              5.4.7.4.18.7 Array.mapWithIndex && .mapWithIndex

              5.4.7.4.18.8 Array.reduce && .reduce

              5.4.7.4.18.9 Array.reduceWithIndex && .reduceWithIndex

              5.4.7.4.18.10 Array.indexOf && .indexOf

              5.4.7.4.18.11 Array.findIndex && .findIndex

              5.4.7.4.18.12 Array.find && .find

              5.4.7.4.18.13 Array.withIndex && .withIndex

              5.4.7.4.18.14 Array.slice && .slice

            5.4.7.4.19 Mapping group operations

              5.4.7.4.19.1 Map.reduce && .reduce

            5.4.7.4.20 Objects

            5.4.7.4.21 Structs

            5.4.7.4.22 Field reference

            5.4.7.4.23 Object.set

            5.4.7.4.24 Object.setIfUnset

            5.4.7.4.25 Object.has

            5.4.7.4.26 Data

            5.4.7.4.27 Maybe

            5.4.7.4.28 Either

            5.4.7.4.29 match

            5.4.7.4.30 Conditional expression

            5.4.7.4.31 Arrow expression

            5.4.7.4.32 makeEnum

            5.4.7.4.33 assert

            5.4.7.4.34 forall

            5.4.7.4.35 possible

            5.4.7.4.36 digest

            5.4.7.4.37 balance

            5.4.7.4.38 getContract

            5.4.7.4.39 getAddress

            5.4.7.4.40 lastConsensusTime and lastConsensusSecs

            5.4.7.4.41 baseWaitTime and baseWaitSecs

            5.4.7.4.42 Time arguments - relativeTime, absoluteTime, relativeSecs, absoluteSecs

            5.4.7.4.43 makeDeadline

            5.4.7.4.44 implies

            5.4.7.4.45 ensure

            5.4.7.4.46 hasRandom

            5.4.7.4.47 hasConsoleLogger

            5.4.7.4.48 compose

            5.4.7.4.49 muldiv

            5.4.7.4.50 sqrt

            5.4.7.4.51 pow

            5.4.7.4.52 Signed Integers

            5.4.7.4.53 Fixed-Point Numbers

            5.4.7.4.54 Anybody

            5.4.7.4.55 Intervals

              5.4.7.4.55.1 Constructors

              5.4.7.4.55.2 Accessors

              5.4.7.4.55.3 Relational Operations

              5.4.7.4.55.4 Arithmetic Operations

              5.4.7.4.55.5 Other Operations

      5.5 Consensus Network Connectors

        5.5.1 Algorand

        5.5.2 Conflux

          5.5.2.1 FAQ

            5.5.2.1.1 How do I run my Reach DApp on CFX TestNet or MainNet?

            5.5.2.1.2 Why is DApp startup very slow? Why do I need to use setQueryLowerBound?

            5.5.2.1.3 How can I use ConfluxPortal with the Reach devnet?

        5.5.3 Ethereum

      5.6 Participant Backends

        5.6.1 JavaScript

          5.6.1.1 Guarantees

        5.6.2 Reach RPC Server

          5.6.2.1 Reach RPC Client Standard Options

          5.6.2.2 Reach RPC Protocol Specification

          5.6.2.3 Reach RPC Protocol Client Implementation Walkthrough

      5.7 Frontend Support

        5.7.1 JavaScript

          5.7.1.1 Types

          5.7.1.2 loader.mjs

          5.7.1.3 Account Handles

            5.7.1.3.1 EVM-specific (Ethereum and Conflux)

            5.7.1.3.2 Conflux-specific

          5.7.1.4 Contract Handles

          5.7.1.5 Network Utilities

          5.7.1.6 Provider Selection

          5.7.1.7 Utilities

          5.7.1.8 ask.mjs

        5.7.2 JavaScript (RPC)

        5.7.3 Python (RPC)

        5.7.4 Go (RPC)

      5.8 Error Codes

        5.8.1 RA0000

        5.8.2 RC0000

        5.8.3 RE0000

        5.8.4 RE0001

        5.8.5 RE0002

        5.8.6 RE0003

        5.8.7 RE0004

        5.8.8 RE0005

        5.8.9 RE0006

        5.8.10 RE0007

        5.8.11 RE0008

        5.8.12 RE0009

        5.8.13 RE0010

        5.8.14 RE0011

        5.8.15 RE0012

        5.8.16 RE0013

        5.8.17 RE0014

        5.8.18 RE0015

        5.8.19 RE0016

        5.8.20 RE0017

        5.8.21 RE0018

        5.8.22 RE0019

        5.8.23 RE0020

        5.8.24 RE0021

        5.8.25 RE0022

        5.8.26 RE0023

        5.8.27 RE0024

        5.8.28 RE0025

        5.8.29 RE0026

        5.8.30 RE0027

        5.8.31 RE0028

        5.8.32 RE0029

        5.8.33 RE0030

        5.8.34 RE0031

        5.8.35 RE0032

        5.8.36 RE0033

        5.8.37 RE0034

        5.8.38 RE0035

        5.8.39 RE0036

        5.8.40 RE0037

        5.8.41 RE0038

        5.8.42 RE0039

        5.8.43 RE0040

        5.8.44 RE0041

        5.8.45 RE0042

        5.8.46 RE0043

        5.8.47 RE0044

        5.8.48 RE0045

        5.8.49 RE0046

        5.8.50 RE0047

        5.8.51 RE0048

        5.8.52 RE0049

        5.8.53 RE0050

        5.8.54 RE0051

        5.8.55 RE0052

        5.8.56 RE0053

        5.8.57 RE0054

        5.8.58 RE0055

        5.8.59 RE0056

        5.8.60 RE0057

        5.8.61 RE0058

        5.8.62 RE0059

        5.8.63 RE0060

        5.8.64 RE0061

        5.8.65 RE0062

        5.8.66 RE0063

        5.8.67 RE0064

        5.8.68 RE0065

        5.8.69 RE0066

        5.8.70 RE0067

        5.8.71 RE0068

        5.8.72 RE0069

        5.8.73 RE0070

        5.8.74 RE0071

        5.8.75 RE0072

        5.8.76 RE0073

        5.8.77 RE0074

        5.8.78 RE0075

        5.8.79 RE0076

        5.8.80 RE0077

        5.8.81 RE0078

        5.8.82 RE0079

        5.8.83 RE0080

        5.8.84 RE0081

        5.8.85 RE0082

        5.8.86 RE0083

        5.8.87 RE0084

        5.8.88 RE0085

        5.8.89 RE0086

        5.8.90 RE0087

        5.8.91 RE0088

        5.8.92 RE0089

        5.8.93 RE0090

        5.8.94 RE0091

        5.8.95 RE0092

        5.8.96 RE0093

        5.8.97 RE0094

        5.8.98 RE0095

        5.8.99 RE0096

        5.8.100 RE0097

        5.8.101 RE0098

        5.8.102 RE0099

        5.8.103 RE0100

        5.8.104 RE0101

        5.8.105 RE0102

        5.8.106 RE0103

        5.8.107 RE0104

        5.8.108 RE0105

        5.8.109 RE0106

        5.8.110 RE0107

        5.8.111 RE0108

        5.8.112 RE0109

        5.8.113 RE0110

        5.8.114 RE0111

        5.8.115 RE0112

        5.8.116 RE0113

        5.8.117 RE0114

        5.8.118 RE0115

        5.8.119 RE0116

        5.8.120 RE0117

        5.8.121 RE0118

        5.8.122 RE0119

        5.8.123 RE0120

        5.8.124 REP0000

        5.8.125 RI0000

        5.8.126 RI0001

        5.8.127 RI0002

        5.8.128 RI0003

        5.8.129 RI0004

        5.8.130 RL0000

        5.8.131 RP0000

        5.8.132 RP0001

        5.8.133 RP0002

        5.8.134 RP0003

        5.8.135 RP0004

        5.8.136 RP0005

        5.8.137 RP0006

        5.8.138 RP0007

        5.8.139 RP0008

        5.8.140 RP0009

        5.8.141 RP0010

        5.8.142 RP0011

        5.8.143 RX0000

    Index